Recently, with the dramatically increasing demand for portable electronic products such as laptop computers, video cameras, mobile phones, and the like, along with the active development of electric vehicles, storage batteries for energy storage, robots, satellites, and the like, research and development for high-performance secondary batteries capable of repeatedly recharging has been actively made. Currently, among commercially available secondary batteries, lithium secondary batteries have little or no memory effect, and thus they are gaining more attention than nickel-based secondary batteries for their advantages of free charging/discharging, low self-discharging, and high energy density.
More recently, secondary batteries are being widely used in not only small devices such as portable electronic products but also medium- and large-scale devices such as vehicles and energy storage systems. In particular, with the steady exhaustion of carbon energy and increasing interest in the environment, the demand for hybrid electric vehicles and electric vehicles is increasing all over the world including United States, Europe, Japan, and the Republic of Korea. In such hybrid electric vehicles or electric vehicles, the most essential component is a battery pack that gives a driving power to an automobile motor. Because hybrid electric vehicles or electric vehicles are supplied with power for driving the vehicles through charging/discharging of battery packs, as compared to vehicles powered by an engine alone, they have higher fuel efficiency and can eliminate or lessen the emission of pollutants, and by this reason, the number of users is now increasing.
When a secondary battery is used for an electric vehicle, to increase the capacity and output, a battery pack is manufactured using battery modules in which many secondary batteries are connected in series and/or in parallel. In this instance, a pouch type secondary battery is widely used in medium- and large-sized devices because it is easy to stack.
FIG. 1 shows a general pouch type secondary battery.
Referring to FIG. 1, the general pouch type secondary battery 1 has a sealing part 30 formed by sealing a pouch case 10 in which an electrode assembly 20 is received, and electrode leads 40, 45 are welded to a positive electrode tab and a negative electrode tab of the electrode assembly 20 respectively and exposed through the pouch case 10. A lead film 50 is interposed between the pouch case 10 and the electrode leads 40, 45.
As shown in FIG. 2, the pouch type secondary batteries 1 are stacked and connected in series and/or in parallel such that the electrode leads 40, 45 provided in each of two adjacent pouch type secondary batteries 1 are connected to a molded product 60, to construct a battery module 11 with improved capacity and output.
Meanwhile, in using the battery module 11 including the plurality of pouch type secondary batteries 1, it is very important to ensure safety. Particularly, in the case of hybrid electric vehicles or electric vehicles on which people ride, there is a concern that an accident may lead to a loss of human life.
Accordingly, a reliability test was conducted to evaluate safety in an impact or vibration situation after the manufacture of the battery module 11. In this instance, however, due to deformation of the electrode leads 40, 45 caused by compression of the battery module 11, as shown in FIG. 3, there is a short circuit risk that will occur at the position ‘A’ between the electrode leads 40, 45 with different polarities not directly connected to each other. In addition, in case that a swelling phenomenon occurs or an external impact is applied while the battery module 11 is used, there is a short circuit risk caused by a contact of the electrode leads 40, 45 with different polarities not directly connected to each other.
When a short circuit occurs due to an electrical contact between the electrode leads 40, 45 provided in adjacent pouch type secondary batteries 1, an overcurrent flows, and accordingly, there is a concern with an accident such as overheat or an explosion of adjacent different pouch type secondary batteries. Therefore, there is a need for an approach to minimize a short circuit risk caused by an unintentional contact between the electrode leads 40, 45 while not greatly changing the existing battery module manufacturing process.
The present disclosure is designed to solve the problem such as the foregoing statements, and therefore the present disclosure is directed to providing an electrode lead for a secondary battery that is less susceptible to cracks and has improved insulation.
The present disclosure is further directed to providing a pouch type secondary battery comprising the electrode lead with high reliability and improved insulation.
The present disclosure is further directed to providing a battery module for preventing a short circuit between electrode leads with different polarities and ensuring safety, manufactured by connecting the pouch type secondary batteries.
These and other objects and advantages of the present disclosure will be understood by the following description.
To achieve the object, an electrode lead for a secondary battery according to the present disclosure is an electrode lead electrically connected to an electrode assembly, and the electrode lead includes a flat metal conductor and a coverlay type insulating film having an exposed shape at an electrically connected part of the metal conductor.
According to an aspect of the present disclosure, the insulating film includes any one material of PI, PET and PEN. The insulating film may be adhered or coated. The exposed shape may be tailored, punched or hot-pressed.
According to another aspect of the present disclosure, the insulating film is a composite film having an adhesive coated on any one film of PI, PET and PEN. In this instance, the adhesive layer is preferably silicone.
According to still another aspect of the present disclosure, the insulating film is formed covering two surfaces of the metal conductor, the exposed shape is formed on two surface of one side of the metal conductor, and on the other side of the metal conductor electrically connected to the electrode assembly, a sealant film layer is adhered from two surfaces of the metal conductor and protrudes from side surfaces of the metal conductor.
The sealant film layer may include one selected from the group consisting of polypropylene, polypropylene chloride, polyethylene, ethylene-propylene copolymer, ethylene-acrylate copolymer, propylene-acrylate copolymer and casted polypropylene, or their mixtures.
To achieve another object, a pouch type secondary battery according to the present disclosure includes an electrode assembly including a positive electrode and a negative electrode with a separator interposed between, an electrode lead electrically connected to each of the positive electrode and the negative electrode and electrically connected to the electrode assembly, and a pouch case in which the electrode assembly is received such that an end of one side of the electrode lead protrudes, wherein the electrode lead includes a flat metal conductor and a coverlay type insulating film having an exposed shape at an electrically connected part of the metal conductor.
In a preferred example, the insulating film is formed covering two surfaces of the metal conductor, and on one side of the metal conductor electrically connected to the electrode assembly, a sealant film layer is adhered from two surfaces of the metal conductor and protrudes from side surfaces of the metal conductor, and the exposed shape is formed on two surfaces of the other side of the metal conductor. Additionally, the pouch case and the electrode lead are thermally bonded with the sealant film layer interposed between.
To achieve still another object, a battery module according to the present disclosure includes a secondary battery stack formed of a stack of pouch type secondary batteries according to the present disclosure, wherein the electrode lead protrudes from the pouch case and has a bent part such that an end is bent to the left or right, the exposed shape of the insulating film of the electrode lead is positioned at flat bottom of the bent part, and the bent parts of the electrode leads of adjacent pouch type secondary batteries overlap, and the metal conductors exposed by the exposed shape are welded to each other.
At least one battery module according to the present disclosure may be combined to manufacture a battery pack. The battery pack may be applied to vehicles.
According to the present disclosure, the coverlay type insulating film of a material with insulation performance such as PI, PET and PEN is applied to the electrode lead to prevent a short circuit from occurring due to an unintentional contact between electrode leads with different polarities, thereby ensuring safety. The exposed shape is applied to part of the insulating film to enable electrical connection such as welding.
The insulating film prevents a short circuit and maintains insulation even though adjacent electrode leads contact each other. Accordingly, there is an effect in improving safety of a pouch type secondary battery and a battery module including the electrode lead.
The insulating film having the electrode lead ensures safety from the external physical impacts and heat generation, and reduces a likelihood that heat generated in the heating process during welding is transferred from the electrode lead to the electrode assembly.
Additionally, the insulating film absorbs or distributes physical forces applied to the metal conductor part of the electrode lead, thereby reducing the cracking of the metal conductor.